1. Field of the Invention
This invention relates to the field of orthopedic surgery and, particularly, to the area of spinal implants for stabilizing the spatial relationship of vertebrae. The device is designed for use in the cervical region of the spine though one skilled in the art may use the device in other regions of the spine and other skeletal fixations.
2. Description of the Prior Art
Spinal plates are well known in the orthopedic art for fixing bones or bone fragments in a pre-selected spatial orientation. The plates are usually attached to the bones or bone fragments by screws designed to make a secure and long lasting connection not affected by the loads caused by normal activities of the host. Gertzbein et al, U.S. Pat. No. 5,620,443, teaches an adjustable cervical connector composed of dual rods spanning the distance between adjacent vertebrae. The rods carry at least two slidable transverse connectors which are attached to the vertebrae by spikes and pedicle screws thereby fixing the relationship of the bones. The connectors are immobilized on the rods by clamps.
Richelsoph, U.S. Pat. No. 6,017,345, teaches a spinal plate spanning the distance between adjacent vertebrae. The plate has screw holes in each end. The pedicle screws are inserted through the holes and allow for some movement.
Shih et al, U.S. Pat. No. 6,136,002, teaches a similar device to that of Gertzbein with the clamps screwed onto the elongated rods.
Published Patent Application US 2003/0060828 A1 to Michelson teaches a cervical plate with at least two plate elements slidably connected together and fixed by a set screw. The contacting surfaces of the plate elements are formed with ratcheting to provide added security.
In all these prior art devices, the plate must be held in the selected position while the securing set screws or other fasteners are put in place and the final assembly is completed. Further, the prior art plates are not used in combination with spinal cages for filling the intervertebral space to compensate for removal of the spinal discs and to provide support for bone growth material and/or bone cement.
What is needed in the art is a dynamic cervical plate system that may be adjusted to length, locked in place to provide compression, and will automatically shorten its length to maintain compression. The system includes spinal cages coupled to the plate which provide intervertebral spacers for excised discs.